1. Technical Field
The present invention relates to a webbing take-up device which takes up a webbing belt which constrains a passenger's body and stores the webbing belt in a spool, and particularly, to a webbing take-up device which has a locking unit which can regulate the rotation of the spool when the spool has rotated in a pull-out direction at an acceleration of a predetermined value or more.
2. Related Art
A webbing take-up device which constitutes a seat belt apparatus of a vehicle includes a locking mechanism which operates at the time of abrupt deceleration or the like of the vehicle. As this type of locking mechanism, there are a so-called “VSIR mechanism” which operates to detect the acceleration (deceleration) when a vehicle decelerates abruptly, and a so-called “WSIR mechanism” which operates when a spool rotates at high speed in a pull-out direction.
For example, in the “WSIR mechanism” in the webbing take-up device disclosed in Japanese Patent Application Laid-Open No. 2008-24284, when a V gear rotates at high speed in the pull-out direction along with the spool, an inertia mass which remains in position due to its inertia consequently rotates in a take-up direction relative to the V gear against the biasing force of a return spring, and the inertia mass which has rotated in the pull-out direction relative to the V gear in this way presses a W pawl. The W pawl pressed by the inertia mass meshes with ratchet teeth formed on an inner peripheral portion of a gear ring, and rotates the gear ring and a sensor gear in the pull-out direction. The sensor gear which has rotated in the pull-out direction oscillates a locking pawl to make the locking pawl engage ratchet teeth of a locking base and lock the locking base which rotates in the pull-out direction along with the spool. This regulates the rotation of the spool in the pull-out direction indirectly.